Alternating current arc welding system



June 21, 1949. sT AL 2,473,917

I ALTERNATING CURRENT ARC WELDING SYSTEM Filed Feb. is, 1948 INVENTORS WITNESSES: 7

fr'ru'lFfzelnerf and Patented June 21, 1949 ALTERNATING "GURRENTARGWELDING SYSTEM "Eniil F. Steinert, Williamsville, and Charles H.

Jennings; Bufi'alo, Y.,-assi gnors to-Wes'tinghouse Electric Corporation, East Pittsburgh, ':-,Pa.-, 41' corporationi' of Pennsylvania "Application February 13, 1948,. Serial No.: 8,254

' 6 Claims. -1 7 Our invention-relates, generally, "to arc'wel'ding systemsi and it has referencein particular to an alternatingcurrent arc welding system of the stabilized-type.

'Generallystated, it is an object of our 'invention to provide an improved stabilized arc welding system, whichis simple and'inexpensive to manufacture, and" which is reliable and effective "in operation.

More'specifically, it is'anobjectof our invention to provide for substantially eliminating undesirable arc noises "in a stabilized alternating Cliill'it arc welding system.

It is also an object of ourinvention' to provide, in an alternatingcurrentarc welding systern embodying ashunt stabilizing capacitor, for "utilizing a relatively "low value 'ofresistan'c'e in series circuit relation w'iththe capacitor ferreducingthe-arc noise without. appreciably affectingfth-e stabilityof the arc.

-'-Another object of our invention is to provide for connecting a resistor of"'approximate1y one ohm 'or less in circuit relation with an I are stabilizing capacitor in an alternating current arc weldingsyst'em.

"Yet an'other objectofour invention is to provide for reducing thetamplitudeeof some of the higher harmonics of the transient arc current in a a" stabilized:- arc welding system, and I thus lower the noise level of the arc.

Other objects will mpart-be obvious, and will in part be described hereinafter.

Impracticing our invention in one of itsfo'rms,

1E a'capaeitor of about 120 'microfarads isconnected across the secondary -Windinjg-of the welding transformer in an alternating current are Welding system,- intermediatethe'usual current limiting reactor and the arc. A resistor on the order of from to 1 ohm is connected in series circuit relation with capacitor to reduce the arc noise without appreciably reducing the effectiveness of the arc stabilizing capacitor.

For a more complete understanding of the nature and scope of our invention, reference may be made to the following detailed description, which may be read in connection with the accompanying drawing, in which the single figure is a diagrammatic view of an alternating current arc welding system embodying the invention in one of its forms.

Referring to the drawing, there is shown an alternating current arc welding system wherein a welding transformer I2 is disposed to supply electrical energy to a welding circuit 14, includa-BU 2 'ingianelec'trode' I5 and work I6 upon whicha welding operation'is to be performed.

The transformer [2 may be of any suitable type "having a'primary winding I! for connection to a suitable source of alternating current power, and a secondarywindin'g l8. The secondary winding may be" connected to supply electrical energy to the welding circuit. l4 at an open circuit voltage on the order of approximately 65 volts. A current limiting reactor I9 maybe connected in the welding circuit I4 in series circuit relation with the secondary winding 'lfland be adjustable to pro- "vide' for'limiting the welding current to different predetermined suitable values. In order to improve the power factor of the weldng system and raiseit'toi asa'ti'sfactory value, the transformer I2 may be'provided with a tertiary winding 20 across which may be connected a capacitor 2|. When used with a 300 ampere welder having a 440 volt tertiary winding, the capacitor 2| may have a valueon the order of microfarads, for example.

"In order to provide for maintaining a reasonably stable'arcbetwe'en the electrode I5 and the work I6;'an arc stabilizing capacitor 25 may be connected across'the welding circuit in shunt circuit'r'elationwith the arc Welding circuit, intermediate'the'reactor l9 and the arc, as shown The capacitor 25 may have a value of from approximately 50 to 150 microfarads, being, for ex- "ample, on 'theorder of microiarads, as disclosed in-"the copending application of Alfred B.

' Whitefi-SerialNo. 713,237, filed on November 30, 1946.

When an' arc stabilizing capacitor is connected across the welding circuit in this manner it in- -duces transient voltages of relatively high fre- "quency across'the arcduring the intervals when the arc current is passing through its zero value and thereby assists in keeping the arc space ionized so as to provide a more stable arc. It has been found, however, that the presence of such an arc stabilizing capacitor greatly increases the noise level of the arc. This increase in noise level is generally characterized by a relatively sharp, crackling sound, which has proven to be objectionable to welding operators even though the stabilized arc may not actually be harmful to them. By connecting a resistor 21 in series circuit relation with the arc stabilizing capacitor 25, the amount of the arc noise produced by the capacitor may be greatly reduced. For example, a resistor having a value of from of one ohm to approximately one ohm has been found to be highly effective in reducing the characteristic noise of a stabilized arc to a very low and entirely unobjectionable level. The effect of such a resistor has been checked over the entire welding current range of from 20% to 125% of the current rating of the welding transformer and has been found to give substantially uniform re sults over the entire operating range. It i believed that the resistor reduces the peak values of transient current produced by the arc stabilizing capacitor, thereby tending to smooth out the transient current wave and reduce or even eliminate some of the higher harmonics present therein. The reduction of these higher harmonics reduces the audible noises of the arc, without appreciably affecting the magnitude of the transient current, and hence the arc stabilizing effect of the capacitor 25.

From the above description and accompanying drawing, it will be apparent that we have provided in a simple and effective manner for improving the operating characteristics of a stabilized alternating current arc welding system. By reducing the level of the heretofore objectionable arc noise, stabilized arc welders are made more attractive to the operator who is enabled to perform more efficiently when using such stabilized arc welding systems. Since the noise level of the arc is reduced without appreciably affecting the stability of the arc, the effectiveness of the arc stabilizing capacitor for all practical purposes is in no way reduced.

Since certain changes may be made in the above-described constructions, and different embodiments of the invention may be made without departing from the spirit or scope of the invention, it is intended that all the matter contained in the above description and shown in the accompanying drawing shall be considered as illustrative and not in a limiting sense.

We claim as our invention:

1. An arc welding system comprising, a welding transformer disposed to supply welding current to a welding circuit, a capacitor connected in shunt circuit relation with the welding circuit intermediate the transformer and the are, and a resistor connected in series circuit relation with the capacitor to reduce the arc noise without appreciably reducing the stabilizing effect of the capacitor.

2. For use with an alternating current arc welding circuit disposed to be energized from a welding transformer for maintaining an electric are, a capacitor of from 55 to 125 microfarads connected in shunt circuit relation with the arc, and a resistance of about one ohm connected in series circuit relation with the capacitor.

3. In an arc welding system, a transformer having a primary winding disposed to be connected to a source of electrical energy, said transformer having a secondary winding and a tertiary winding, a capacitor connected across the tertiary winding to improve the power factor of the system, an arc stabilizing capacitor connected in shunt circuit relation with the secondary winding to provide a transient arc stabilizing current, and a resistance element connected in series circuit relation with the stabilizing capacitor to reduce the higher harmonics of the transient stabilizing current.

4. The combination with a, transformer having a primary winding for connection to a source of alternating current, a secondary winding disposed to have an open circuit voltage on the order of volts disposed to supply electrical energy to an arc and a tertiary winding, of a capacitor connected across the tertiary winding to correct the primary power factor, an arc stabilizing capacitor of approximately microfarads connected in shunt circuit relation with the arc to produce a transient arc current, and a resistor of about one ohm resistance connected in series circuit relation with the arc stabilizing capacitor to reduce harmonics of the transient arc current in the audible range.

5. For use with a transformer disposed to supply alternating current to an arc welding circuit, an arc stabilizing capacitor connected in shunt circuit relation with the arc, and a resistance element connected in series circuit relation with the capacitor to substantially reduce the arc noise without materially reducing the stabilizing effects of the capacitor.

6. An arc welding system comprising, a transformer disposed to supply electrical energy to a welding circuit, a reactor connected in series circuit relation with the transformer and the welding circuit, an arc stabilizing capacitor of approximately 120 microfarads connected in shunt relation with the welding circuit intermediate the reactor and the arc, and a resistor of less than one ohm connected in series circuit relation with the capacitor to minimize the arc noise.

EMIL F. STEINERT. CHARLES H. JENNINGS.

REFERENCES CITED The following references are of record in the 50 file of this patent:

UNITED STATES PATENTS Number 

